Insulating glass units are formed generally of a pair of glass panes that are generally parallel to one another and that have a spacer running between them at their peripheries. Spacers, commonly of metal, are adhered by means of a sealant to the glass panes, the sealant desirably forming a gas-tight seal to thus prevent air or other gas from entering or leaving the space between the panes. Insulating glass units are shown, for example, in U.S. Pat. Nos. 5,377,473 and 5,439,716.
To improve the insulating capacity of such glass units, the between-pane space may be filled with argon or other gas that has a coefficient of thermal conductivity less than that of air. Commonly, the between-pane space is filled with argon to a pressure that is approximately atmospheric, although pressure adjustments may be made in connection with the elevation of the geographic locale where the insulating glass unit is to be installed. The periphery of an insulating glass unit is encased in a frame which may be of wood or other material, and the wooden frame in turn may have a weather-resistant plastic coating.
Over a period of time, argon may slowly leak from the between-pane space to the atmosphere. This occurs at a rate greater than the permeation of oxygen or nitrogen into the between-pane space, with the result that the pressure in the between-pane space is reduced below atmospheric pressure. The resulting pressure differential causes the panes to cup inwardly, and the panes can eventually touch near their centers, with consequent loss of insulating value. In some cases, the cupping of the panes is so great as to cause one or the other of the panes to shatter. When failure occurs, the window units necessarily have to be replaced, and this can be extremely expensive in that the failed window unit must be removed, replaced, and reinstalled on a unit-by-unit basis.
When transported to geographic locations of higher elevation and hence reduced atmospheric pressure, the panes of insulating glass units may bulge outwardly under the pressure differential across the panes, and this also causes distortion of the panes and may lead to ultimate glass breakage.
It would be desirable to provide a method and apparatus to enable insulating glass units that bulge or that have become cupped to be repaired without requiring them to be removed from the frames within which they are encased, and without requiring them to be removed from the buildings in which they are installed.